Circuit breaker



July 23, 1935. .1. G. JACKSON 2,009,050

CIRCUIT BREAKER Filed April 24, 1955 5 Sheets-Shea; 1

3 Sheets-Sheet 2 July 1935- J. G. JACKSON CIRCUIT BREAKER Fild April 24,1955 7 W r3 M R 4 F N H fl aw w Q July 23, 1935. J JACKSON 2,009,050

CIRCUIT BREAKER Filed April 24, 1933 3 Sheets-Sheet 3 C URFE N 771 1! AMP5 RES Patented July 23, 1935 PATENT OFFICE CIRCUIT BREAKER John G.Jackson, Detroit, Mich., assignor to Square D Company, Detroit, Mich., acorporation of Michigan Application April 24, 1933, Serial No. 667.696

22 Claims.

The invention relates to circuit breakers and I has for its object theobtaining of a construction adapted for, first, automatically andeifectively rupturing high values of current; second, selective 5operation under various conditions of current flow. It is a furtherobject to obtain a construction which will conform to theinternationally accepted requirements of the National Board of FireUnderwriters and Underwriters Laboratories. .To this end the inventionconsists in various features of construction as hereinafter set forth.

One of the features of my invention is the means employed forsuppressing the are formed on the breaking of contacts. For this purposeI make use of suppressor plates and magnetic deflection which haveheretofore been used for such purpose. I have, however, designed aconstruction which is much more effective in its operation and which inaddition to arc suppression protects or guards against welding of thecontacts and is exceedingly simple in construction.

Another feature of my invention is the means employed for selectiveoperation. This comprises essentially an automatic circuit breaker, alatch for holding the same normally in closed position, and athermostatically operated releasing means for said latch adapted forsubstantially instantaneous operation in case of short circuiting andfor operating with a small time lag in case of relatively heavyoverloads and for delayed operation in case of non-dangerous overloads.For instance where used to control a motor, an overload may be carriedfor a brief interval during starting of the motor without releasing thelatch but if continued for a longer period will effect the release.

My improved construction is adapted for various uses, but asspecifically described and illustrated is a three-pole circuit breakersuch as adapted for use in connection with apparatus operating uponthree phase electrical currents.

In the drawings:

Fig. 1 is a plan view of the switch with the cover of the housingremoved;

Fig. 2 is a cross section on line 2-2 of Fig. 1;

Fig. 3 is a section on line 3-3 of Fig. 1;

Fig. 4 is an end elevation of the swltgxcly Fig. 5 is a similar viewshowing parts in a different position of adjustment;

Fig. 5A is a sectional elevation illustrating the construction ofbi-metallic thermostatic bars.

Fig. 6 is a section on line 8-6 of Fig. 1;

Fig. 7 is a perspective view showing the contact with magnetic deflectorand the arc deflecting housing therefor removed;

Fig. 8 is a section through said contact and Fig. 11 is a graph showingthe characteristic curves respectively for the self-heating thermostaticelement and the indirectly heated thermostatic element.

As shown, A is an insulator base plate for the circuit breaker on whichare mounted thesta tionary contacts B, B, B and the cooperating movablecontacts C, C, C which latter are carried by a rockable insulator memberD pivotallymounted in a bracket E on the base A. A torsion spring Fsleeved upon the pivot pin F in the bracket E serves to resiliently holdthe member D in open position. There is also a manually operable handleG pivotally secured upon a bracket G connected by toggle links H, H to abracket H on the rockable member D forming a means -i'or closing thecircuit and holding the contacts locked in closed position against thetension of the spring F. g

F0! are suppression and for guarding against welding of the stationaryand movable contacts to each other, I have devised the following con--.struction:

Each of the stationary contacts B, B, 13 is formed of a bar of highelectrical conductivity such as copper and preferably bent intosubstantially U form. The base portion 13 is secured to the base A andis provided with a connector clamping screw B The top portion B isparallel to the base B and has secured thereto a U- shaped member I ofiron or other magnetic material having parallel legs I, I and acomparatlvely narrow slot or space therebetween. Filling this space isan upwardly extending tongue B which is substantially flush with theupper face of the member I and forms the contact face for bearingagainst the movable contact member-.C. The latter is also preferablyformed of a flat bar of copper or other conductive material which istwisted to have an outer end portion C extending in a vertical planeabove the tongue 13 and a horizontal portion 0, the end of which restsupon the rockable member D. At the end of the portion C is a downwardlyprojecting tongue B engaging a recess in the member D to retain thecontact from lateral displacement and intermediate the ends of themember C is a spring J sleeved upon a pin J which passes upward throughthe member D and bar C and has'a detachable collar or abutment J for thespring at its upper end. The arrangement is such that in the closedposition of the contacts the portion C will be at an oblique angle tothe member D, the spring J being tensioned to hold the portion C againstthe portion B. This also permits an acceleration'of the member D duringopening movement before it lifts the contact C from the cooperatingcontact to impart an initial higher velocity thereto.

Mounted on the member B is a casing formed of electrical insulator andheat resisting material and which comprises a pair of plates K Kparallel to each other on oppomte sides of the portion C and above theportions 1, I of the member I. This casing is also provided with aportion K which surrounds the member B and the end portion of the memberI exposing only the portion 8. A spring clip K secured to the base A andembracing the casing serves to hold the same from displacement. Thuswhen the metalliccircuit is broken by the separation of the member Cfrom the tongue portion B the continued flow of current through the arcwill develop a mag- 'netic field which operates to deflect the areoutward between the plates K and K and away from the member C The tongueB may be formed of the same material as the member B but to avoid dangerof melting and welding I preferably form this tongue of an electricallyconductive but heat resistant material. Thus silver maybe used for itshigh electrical conductivity and may be alloyed with some high fusingmetal such as tungsten or molybdenum, or other similar metals. The smallamount of material required for making the tongue will permit the use ofsuch expensive metals without greatly adding to the cost of thestructure.

As above stated, the contacts. C, C, C may be manually closed againstthecontacts B, B, B

by the operation of the handle G and when closed will be locked in thisposition by the straightening of the toggle links H H. The automaticrelease of this look under various conditions is efiected by mechanismof the following construction:

Projecting from the base plate A are posts L, L, L, L on which areslidably mounted insulator blocks M and M. N is a bar preferably ofinsulating material extending between the blocks M and M and provided atits opposite ends with projecting fingers N which loosely engagebearings N on'lugs M projecting from said blocks M and M. The bar Npasses beneath a bent link N connected at one end to the common pivot ofthe links H and H and at its other end having a hooked engagement with apin N on the post or bracket G, but yieldably held in engagementtherewith by a spring N L are springs sleeved upon the posts L, L, etc.beneath the blocks M and M acting to lift said blocks and through themedium of the connecting bar N to lift the bent link N so as to breakthe toggle joint and permit the spring F to open the circuit breaker.Such operation is normally prevented by latch lugs for holding theblocks M and M from upward movement and which are only released undercertain conditions of current flow.

As above stated, the conditions under which the circuit breaker shouldoperate are, first, in case of a short circuit and second, in case of anoverload which is not objectionable for a short-time interval but shouldnot be carried for a longer period. For the performance of each of thesefunctions I employ a thermostatic element which i is'heated to operatingtemperature by the excess current. However, for the first function theoperation should be as nearly instantaneous as possible whlle for thesecond function a definite the increased volume of current willinstantaneously generate heat for its operation. On the other hand, forthe second function the heat generated by the increased flow of currentindirectly afiects the thermostatic element so as to produce a lag ofthe desired duration.

Various constructions of thermostatic elements and latch locks may beemployed, but as shown in Fig. 4 the construction is as follows:

O is a post projecting laterally from the block M and on which isrevolubly mounted a toothed wheel 0'. P and P are bi-metallicthermostatic bars secured at their lower ends to the base A andextending upward on opposite sides of the toothed wheel 0'. P areshoulders formed upon the bars PP adapted to engage the diametricallyopposite teeth of the wheel 0 to hold said wheel from rotation in eitherdirection and to also hold the block M in depressed position against thetension of the springs L One of the bl-metallic bars P is directlyconnected into the electric circuit of one of the poles of the circuitbreaker when the latter is in closed position. This circuit as showncomprises a conductor Q connecting the movable contact C with a post Qpassing through the base A and a conductor Q connects the post Q with apost. Q passing upward through the plate A and connected to the base ofthe bi-metallic bar P'. The upper end of the bar P is connected by aflexible conductor Q with a resistor conductor R arranged parallel tobut out of contact with the bi-metallic bar P. The opposite end of theresistor R is connected to theterminal post R through which thecirthrough the flexible conductor Q and resistor R to the terminal postR. If the volume of current thus flowing is below a certain limit, theheat generated in the bi-metallic bar P and resistor R'will not besuflicient to produce a re-' lease. If, however, there is a shortcircuit, then the heat directly generated in the bi-metallic bar P willcause the lateral deflection of said bar so, as to release theshoulolerl? from the toothed wheel 0 whereupon said toothed wheel ispermitted to revolve, disengaging from the shoulder P of the bar P andpermitting the springs L to lift the block M. This in tumwill raise oneend of the bar N, carrying upward with it the bent link N so as to breakthe toggle joint and permit the spring F to open the circuit breaker.,The volume'of current required to produce this effect is relativelylarge and for lesser overloads the heat generated in the bar P may notbe sufllclent to release said bar from the toothed wheel 0'. However,the resistor R will be transferred by radiation-or conduction to thebi-metallic bar P and after a definite time. in-

'cuit breaker is connected into the external cirgenerate heat by thislimited overload which will te'rval will warp said bar suiiiciently torelease the wheel 0' from the shoulder P whereupon the circuit breakerwill open. Thus the two thermostatic elements P and P are simultaneouslyaffected by an overload but one will respond substantiallyinstantaneously to a short circuit and with a small time lag to arelatively large overload above a predetermined limit without operativeresponse below said limit, while the other will respond to an overloadbelow said limit but with a greater time lag.

A modified construction is vshown in Fig. 9. '5

This comprises the post 0 and toothed wheel 0', thermostatic bi-metallicbar P and shoulder P engaging one side of the wheel, the same as in theconstruction previously described. Instead, however, of providing asecond bi-metallic bar upon the opposite side of the toothed wheel, asecond toothed wheel S is arranged to engage the toothed wheel 0'. Thislatter toothed wheel is fixed upon a pin S which extends into a solderpot S mounted upon a resistor T which is connected in to the electriccircuit in series with a bi-metaliic bar P. The resistor T is mountedupon posts U rising from thebase A and so positioned as to hold thetoothed wheel S in engagement with the toothed wheel 0, while the pin Sis held from rotation by the solidified solder in the pot S With thisconstruction the operation under short circuit or excessive overload isthe same as previously described, releasing the shoulder P from thetoothed wheel 0 and permitting said wheel to turn so as to disengagefrom the toothed wheel S. For limited overloads, the shoulder P will notbe released from the toothed wheel 0' but the heat generated in theresistor T will after a certain time interval melt the solder in the potS permitting the pin S to revolve and with it the toothed wheel S. Thiswill release the toothed wheel 0 and efiect the opening of the circuitbreaker.

It is obvious that the specific constructions of latch releasing meansabove described may be variously modified. The essential feature is thatthe release is effected alternatively by a plurality of thermal means,one responding substantially, instantaneously to a heavy overload, butproviding ,a characteristically longer interval before tripping forlighter overloads, while the other iers from the characteristicoperation of the first mentioned thermal means. 1

The are suppressing means is exceedingly simple in construction andefiective in operation. It will be noted that the U-shaped magneticmemher is completely protected by the insulator housing and at the sametime the legs of the u extend in fairly close proximity to each other.This will develop a strong magnetic field which reacts upon the arc toexpel it in an outward direction away from the contacts C and B Thecircuit breaker is preferably enclosed in a casing V, the cover of whichis apertured for the passage of the manually operable handle G. Theblocks M and M are also provided with outwardly extending posts M whichpass through apertures in the cover and serve as means for re-settingthe catch after the automatic release of the circuit breaker. When thecatch is reset, the circuit closer may be closed by moving the handle Gto the left, Fig. 2, from its dotted to its full line position. Duringthis movement the link N will hold the toggle links H H from swingingupward so that the member D will be rocked to closed position and saidlinks straightened and locked..

Fig. 11 is a graph illustrating the characteristics of the self-heatingthermal unit by the curve Y and of the indirectly heated thermal elementby the curve X. It will be noted that for a current volume of 44amperes, the tripping of the circuit breaker will occur in the same timein each of these curves; viz: in 17 seconds. For lesser current volumes,the element represented by the curve X will be the first to operate, but

for higher current volumes the element represented by Y will operatefirst. Thus for amperes the element Y will release in one second,whereas the element X would require five seconds for release. Thus whereboth elements are used, the element X will be the first to operate up to44 amperes and the element Y will be first for all higher currentvolumes.

The specific construction of switch shown and described is a three-poleswitch and consequently it is essential to protect the circuits on eachside of the central pole. For this reason the automatic releasingmechanism is in duplicate, one of said mechanisms responding toconditions in the circuit on one side of the central pole and the otherresponding to conditions in the circuit on the opposite side of saidcentral pole. Either one of these mechanisms will throw the switch, asthe lifting of one end of the bar N will actuate the link N, to breakthe toggle joint. Where, however, a two-pole circuit closer is used, asingle releasing mechanism is all that is necessary.

What I claim as my invention is:

1. In a self-contained circuit breaker unit, the combination with fixedand movable contacts and resilient means for automatically separatingthe same, of means for restraining the operation of said automatic meansto hold said contacts in closed position, and a plurality of releasingmeans for said restraining means, each comprising an electrically heatedthermostatic element selected with respect to different overload currentvalues, the thermostatic element responsive to the higher current valuebeing self-heated thereby and the thermostatic element responsive to thelower current value being indirectly heated thereby to have a greatertime lag in its operation.

2. In a self-contained circuit breaker unit, the combination with fixedand movable contacts and resilient meansfor automatically separating thesame, of means for restraining the operation of said automatic means tohold said contacts in closed position, and a plurality of releasingmeans for said restraining means, each comprising a bimetal thermostaticbar and one of said bars being in series circuit with said contacts andresponsive to large overload current values, and a resistor in indirectheat communication relation to the other of said bi-metal bars, also inseries circuit with said contacts and responsive to lower overloadcurrent values.

3. In a circuit breaker, the combination with fixed and movable contactmembers, of resilient means for automatically separating said membars, acatch for restraining operation of said resilient means to hold saidcontact members in closed relation, said catch comprising a rotatabletoothed wheel secured to the movable member and detents engaging teethon the opposite sides of the axis of said wheel to restrain the samefrom either rotative or bodily movement, means responsive to differentoverload current values for withdrawing the detents on opposite sides ofsaid wheel whereby the withdrawal of either detent will release saidcatch, and means for delaying the withdrawal of the detent by the meansresponding tothe lower overload current value.

4. In a circuit breaker, the combination with fixed and movable contactmembers, of resilient means for automatically separating said members,

4 a catch for restraining operation of said resilient means to hold saidcontact members in closed relation, said catch comprising a rotatabletoothed wheel secured to the movablemember and detents engaging teeth onthe opposite sides oiiahe axis of said wheel to restrain the same fromeither rotative or bodily movement, means responsive to differentoverload current values for withdrawing the detents on opposite sides ofsaid wheel, whereby the withdrawal of either detent willrelease saidcatch, the means responding to the higher current value consisting of abi-metal-1 110 bar directly connected in series circuit with saidcontacts and the other of said means including a resistor and athermostatic element indithermostatic bar connected to-eachdetent and.

adapted to withdraw the same on the heating of said bar to apredetermined temperature, means for connecting one of said bars inseries circuit with said contacts to eiiect the heating of the bar by anoverload current of large value, and an electrical heater also in serieswithsaid contacts and in indirect heat communicating relation totheother of said thermostatic bars responsive to overload current ofsmaller value to cause withdrawal of the detent after a predeterminedtime interval.

6 In a circuit breaker, the combination with fixed and movable contactmembers, of resilient means 1' or automatically separating said members,

a catch for restraining operation of said resilient means to hold saidcontact members in closed relation, said catch comprising a rotatabletoothed wheel secured to the movable member and detents engaging teethon the opposite sides of the axis of said wheel torestrain the same fromeither rotative or bodily movement, means responsive to differentoverload current values for withdrawing the detents on opposite sides ofsaid wheel whereby the withdrawal of either detent will release saidcatch, each of said means comprising a bi-metallic thermostatic bar towhich the detent is attached, the bar in the means responding to thehigher current value being directly connected in series circuit withsaid contacts, and a resistor also in series circuit with said contactsin heat communicating relation to the other of said bars to actuate thesame with a predetermined lag.

'7. In a circuit breaker the combination with fixed and movable contactmembers, of resilient means for automatically separating said members, acatch for restraining operation of said resilient means to hold saidcontact members in closed relation, said catch comprising a rotatabletoothed wheel secured to the movable member and detents engaging teethon the opposit'sides of the axis of said wheel to restrain the same fromeither rotativeor bodily movement, means responsive to difierentoverload current values for withdrawing the detents on opposite sidesofsaid wheel whereby the withdrawal of either detent will release saidcatch, the means responding to the higher current value comprising abi-metal thermostatic bar connected to the detent and in direct seriescircuit with said contacts, and the other of said means including afusible connection with said detent and an electric heater in heatcommunicating relation to said fusible member and included in seriescircuit with said contacts,

8. In a circuit breaker, the combination with fixed and movablecontacts, of a rockable member carrying said movable contact,=resilientmeans for automatically rocking said member to separate said contacts,manua-lly operable means for rocking said member to close said contactsincluding a toggle jointed brace which locks in the closed position ofthe contacts, a resiliently operated trip for unlocking said brace topermit automatic separation from said contacts, a catch for restrainingsaid, trip from operation including a toothed wheel revolubly mountedthereon,

and detents for engaging teeth on oppotacts, and the other of said meansincluding a -thermostatic element and an electrical heater in indirectheatcommunicating relation thereto, said heater being also included inseries circuit with' said contacts.

9. In a circuit breaker the combination with fixed and movable contacts,of a rockable member for carrying said movable contact, resilient meansfor rocking said member to separate said contacts, manually operablemeans for rocking said member to close said contacts, said meansincluding a toggle Jointed brace for locking the contacts in closedposition, a trip for said brace includln'g a slidable block operativelyconnected thereto, resilient means for propelling said block, a catchfor restraining said block from movement including a toothed wheelrotatively mounted on the block and detents engaging teeth on oppositesides of the axis of said wheel to hold the same from either rotative orbodily movement, means responsive to different overload current valuesfor respectively withdrawing said detents, one of said means including abi-metal thermostatic bar attached to the detent and directly connectedin series circuit with said contacts, and the other of said meansincluding thermostatic means for withdrawing the detent, and anelectrical heater in indirect heat communication therewith and alsoincluded in series circuit with said contacts.

10. In a circuit breaker, the combination with fixed and movable contactmembers, of resilient means for automatically separating said members, acatch for restraining the operation of said resilient means to hold saidcontact member in closed relation, said catch comprising arotatabletoothed wheel secured to the movable member and detents engaging theteeth of said wheel on opposite sides of the axis thereof to ,restrain.site sides of said wheel whereby the disengagement of either detentwill release said catch, one of said means comprising a bi-m'etallicthermostatic bar to which the detent is attached, said sistor. will fusethe metal in said socket and permit turning of said toothed wheels.

11. An electro-thermally released catch for automatic circuit breakerscomprising a toothed wheel revolubly mounted on the movablemember ofsaid circuit breaker, a detent engaging a tooth on one side of saidwheel, a second toothed wheel engaging the opposite side of said firsttoothed wheel, a shaft connected to said second toothed wheel, a socketfor receiving said shaft, fusible metal in said socket for normallyholding said shaft and toothed wheel from rotation, electro-thermalmeans responsive to a high overload for withdrawing said detent, andelectro-thermal means responsive to a lower overload continued for apredetermined time interval for heating said socket to melt the fusiblemetal therein.

12. A self-contained circuit breaker unit tom prising separable contactsand means for effecting automatic separation of said contacts, saidmeans including a self-heated thermostatic element connected in serieswith said contacts, a resistor also connected in series with saidcontacts and a second thermostatic element heated by said resistor.

13. A self-contained circuit breaker comprising separable contacts andmeans effecting automatic separation of said contacts, said meansincluding a self-heated bi-metal thermostatic bar connected in serieswith said contacts, a resistor also connected in series with saidcontacts and a second bi-metal thermostatic bar heated by said resistor.

14. A self-contained circuit breaker unit comprising separable contactsand means for effecting automatic separation of said contacts, saidmeans including a self-heated bi-metal thermostatic bar connected inseries with said contacts, a resistor also connected in series with saidcontacts and a second thermostatic element including a fusible holdingmeans heated by said resistor. I

15. A self-containedcircuit breaker unit including separable contactsand a plurality of means for effecting automatic separation of saidcontacts, one of said means, responsive to large over-load currents,comprising a self-heated thermostatic element connected in series withsaid contacts and another of said means, responsive to sustained, lowerover-load currents, comprising a thermostatic element indirectly heatedby a resistor connected in series with said contacts and said firstelement.

16. A self-contained circuit breaker unit including separable contactsand a plurality of means for effecting automatic separation of saidcontacts, one of said means, responsive to large over-load currents,comprising a self-heated bimetal thermostatic bar connected in serieswith said contacts and another of said means, responsive to sustained,lower over-load currents, comprising a bi-metal thermostatic barindirectly heated by a resistor connected in series with said contactsand said first element.

17. A self-contained circuit breaker unit including separable contactsand a plurality of means for effecting automatic separation of saidcontacts, one of said means, responsive to large holding meansindirectly heated by a resistor connected in series of said contacts andsaid first element.

18. A self-contained circuit breaker comprising separable contacts and aplurality of means for effecting automatic separation of said contacts,one of said means comprising a self -heated, series connectedthermostatic element operating with moderate time lag in response toheavy over-loads and another of said means comprising a series connectedresistor element and a thermostatic element indirectly heated therebyand operating in response to sustained, moderate over-loads.

19. A self-contained circuit breaker comprising in combination separablecontacts and a plurality of means for effecting automatic operation ofsaid contacts, one of said means comprising a self-heated thermostaticelement having a time lag characteristic corresponding to therequirements for protection from heavy over-loads and another of saidmeans comprising an externally heated thermostatic element having a timelag characteristic corresponding to the requirements for protection fromsustained moderate overloads.

20. In a three-pole circuit breaker, the combination of separablecontacts, resilient means for different poles of said breaker, each ofsaid units comprising a plurality of thermostatic means, one of saidthermostatic means comprising a self-heated, series connectedthermostatic element and another of said thermostatic means beingindirectly heated by a series connected resistor element.

21. A self-contained circuit breaker equipped for circuit and motorprotection comprising in combination separable contacts and a pluralityof means ,for effecting automatic separation of said contacts, one ofsaid means comprising a self-heated thermostatic element having a timelag and current characteristic corresponding to the requirements forcircuit protection and another of said means comprising an externallyheated thermostatic element having a time lag and current characteristiccorresponding to the requirements for motor protection.

22. In a self-contained circuit breaker unit equipped for circuit andmotor protection, the combination with fixed and movable contacts andresilient means for automatically separating the same, of means forrestraining the operation of said automatic means to hold said contactsin closed position, and a plurality of releasing means for saidrestraining means, each comprising an electrically heated thermostaticelement selected with respect to time lags at different current values,the thermostatic element for circuit protection, responsive to thehigher current values, being self-heated thereby and the thermostaticelement for motor protection, responsive to the lower current values,being indirectly heated thereby to have a greater time lag in itsoperation.

JOHN G. JACKSON.

